Bathtub install--finishing

Hello all,
I'm replacing my bathtub and have a couple of questions about my finish work. The tub surround will be acrylic and we just plan on painting between the top of the surround and the ceiling. The tub sits in an alcove with the ceiling dropped down. I have to raise the ceiling up (or stoop every time I shower) but it will still be a bit lower than the ceiling in the rest of the bathroom. I plan on using green board for the ceiling and the walls down to the surround. I assume I'll need a vapor barrier behind the green board? Plastic ok or should I use roofing felt? I'll just staple it to the studs--ok? Do I need special screws for the green board? And is there a good way to seal the seams between the ceiling and walls to keep moisture from getting behind the green board? Should I insulate behind the green board? All three walls of the alcove are interior. What about insulating above the ceiling? There will be maybe a foot of space between the alcove ceiling and the attic insulation above it.

I'd consider using cement board - cbu. Greenboard has a water repellant surface, but when you drive screws through it, it is nearly the same as drywall. For a vapor barrier, you can use either the roofing felt or plastic sheeting. Just staple it to the studs. Assuming the tub has a tiling flange or some sort of flange around the alcove sides, run the vapor barrier down over that flange on the inside of the tub and cut it off so it won't show prior to installing the sides.

The ceiling is not considered a wet area in a shower unless it is a steam shower. Greenboard is not required, and actually isn't as strong as plain drywall. If used, it should be strapped so it can be screwed in at 12" spacing, not the 16" in normal joists. If you prime and paint it well, and have ventilation in the bathroom, it will last as long as greenboard with fewer problems and isn't as likely to sag.

Do a google on greenboard ..... best to avoid it. Even though i have some in my recent build (see link below) I at least have cement board covering area's of direct water contact. Had i know more i would have insisted on cement board from floor to ceiling on every wall ..... i don't even think the cost of cement board and labour would amount to much more!!!

a lot depends on your local climate, local building practices, how your house was built, whether or not your house has --or will have-- a humidity problem because of the occupants' living habits, and what your personal standards are, before anyone can tell you yes or no that you "need" a vapor barrier in this location.

steam rising to a ceiling usually doesn't cause experts to demand a vapor barrier. Just F.Y.I.

on the other hand, if you want this to be a good installation and you are not pressed to finish this as soon as possible, you can do it and no-one will put you down for it. Rather, they will praise you for your good work and high standards.